This invention relates to RF network analyzers and more particularly to a method for removing phase errors generated in measurement signals resulting from movement of the cable connected between the device under test and the source of RF signals.
Characterizing various components and circuits within a particular frequency domain is critical in both the design and testing of electronic circuits. Only by knowing the phase characteristics of each such component or circuit can one be certain of meeting required objectives. Significant progress has been made in the prior in the development of network analyzers to characterize various aspects of circuits and components. However, a significant problem still remains. Subsequent to calibration of the system the cable which is utilized to interconnect the signal source to the device under test is moved, at least to some extent, while disconnecting the calibration circuit and connecting the device under test. At the time of calibration traditionally both the calibration circuit and cable are measured. Thus any change in the shape or position of the cable destroys the accuracy of the calibration. This inaccuracy can be as much as 100 times error compared to the accuracy of the remainder of the system.
To attempt to compensate for this error the operators of network analyzers have excercised extreme care to minimize movement of the cable when disconnecting the calibration circuit and connecting the device under test thereto. Also the suppliers of the cables have provided different and better cables which has assisted in further decreasing the errors which have been experienced. However, irrespective of the improvement in the cable and the care exercised by the operators, errors on the order of 2% to 3% still exist.